ASHRAE Standard 118.1 provides test procedures for rating directly heated commercial service water heating equipment.

The revised 2022 edition of the standard:

• Updated the scope to be consistent with the Department of Energy's July 11, 2015, final rule that establishes new definitions for "commercial" and "residential duty commercial" water heaters.
• Revised the definition of "heat-pump water heater."
• Updated the classification for Type III water heaters.
• Section 7.2, "Water Piping," was updated and defined visually in Figures 1 through 14.
• Updated venting requirements.
• Reviewed and revised all equations as appropriate for I-P and SI units.
• Revised apparatus for testing AS-HPWH with ducted discharge air.
• Revised test tolerances (Table 1).
• Updated supply water temperatures for testing heat pumps (Table 3).
• Revised test methods and calculations for all heat-pump water heaters (including air source) to be steady state, consistent with Types I, II, and III water heaters.
• Updated setting outlet water temperature for heating capacity for Types 1 through V water heaters.
• Added water heaters with multiple outlet water connections.
• Added new standby loss test method and calculations for Types II and III water heaters.
• Updated references and appendices.